If the "title" metadata element is nonexistent, EPUBReader fails to load the book.

Yes, epubs like this are against the epub spec. But EPUBReader should still be able to open them. I create a lot of test epubs while developing Sigil, and I usually don't bother adding metadata. It would be nice if EPUBReader could handle these.

It would also be great if I could use the left and right arrow keys to trigger the two green buttons at the bottom for changing chapters.

Otherwise this is an amazing extension to Firefox. I truly mean that. I need access to various epub readers, and this one uses Gecko (since it's Firefox), which makes it a nice addition to my testbed. It also has a nice, simple UI and it's very fast. And it works in full-screen mode!

If the "title" metadata element is nonexistent, EPUBReader fails to load the book.

Yes, epubs like this are against the epub spec. But EPUBReader should still be able to open them. I create a lot of test epubs while developing Sigil, and I usually don't bother adding metadata. It would be nice if EPUBReader could handle these.

The new version 1.2.3 which handles this now, is available at the Mozilla website. To force the update, go to the Firefox menu "Tools/Addons" and click on "update".